Topic 5 - Treating Disease

Question 1

What is an antibiotic?

Answer 1

● A substance that kills or inhibits the growth of
bacteria (no effect on viruses)
● No effect on cells in the host organism
● Produced by living organisms e.g. fungi

Question 2

Describe how ‘target’ molecules for new

medicines can be identified

Answer 2

● Comparisons of the genomes of unaffected
individuals and those who are affected by a disease
to identify potential disease-causing alleles
● The alleles themselves or the proteins that they code
for can be used as a target

Question 3

Outline the stages of drug development

Answer 3

1. Screening for potential drugs
2. Preclinical trials
3. Clinical trials
4. Approval by a medical agency

Question 4

Describe the process of screening

Answer 4

● Uses a machine to test large libraries of chemical
substances
● Enables identification of pre-existing chemicals which may affect the target molecule
● Chemicals may be altered, allowing scientists to produce a drug that reacts with target molecules in a specific way

Question 5

What do preclinical trials involve?

Answer 5

● Drug tested on cultured human cells and using
computer models to determine its toxicity (potential to cause damage) and efficiency
● Drug then tested on live animals to establish a safe
dose for humans and observe any side effects

Question 6

What happens during clinical testing?

Answer 6

● The drug is first tested on healthy human volunteers to
ensure that it is safe to use and has no other unwanted
effects on the body
● Drug then tested on patients with the disease to determine
its efficacy. Dosage is slowly increased until an upper limit is established. Optimum dosage is found.

Question 7

What are placebos?

Answer 7

A substance that appears just like the real drug but has no effect on the
recipient

Question 8

What is a blind trial?

Answer 8

● Where the participants don’t know whether they are receiving the new drug or the placebo
● Prevents the patient’s bias affecting the results

Question 9

What is a double-blind trial?

Answer 9

● Neither the participants nor the doctors know who is receiving the new drug or the placebo
● Prevents bias from doctors when analysing the results

Question 10

What is the problem associated with using placebos on patients with a
disease?

Answer 10

Is it ethical to prescribe a sick patient with a placebo knowing that it will not help their condition improve?

Question 11

What are monoclonal antibodies

Answer 11

● Antibodies that are clones from one parent cell

● Specific to one type of antigen

Question 12

Describe how monoclonal antibodies are

produced

Answer 12

1. Specific antigen injected into an animal
2. B-lymphocytes producing complementary antibodies extracted
3. B-lymphocytes fuse with myeloma cells to form hybridoma
   cells
4. Hybridoma cells cultured
5. Monoclonal antibodies collected and purified

Question 13

What are myeloma cells?

Answer 13

Type of tumour cell

Question 14

Outline the uses of monoclonal antibodies

Answer 14

● Detection of pathogens
● Location of cancer cells and blood clots
● Treatment of cancer
● Used in pregnancy test kits

Question 15

What do pregnancy kits test for?

Answer 15

hCG in urine

Question 16

What does a pregnancy test consist of?

Answer 16

A stick containing monoclonal antibodies (mAbs) specific
to hCG:
● mAbs attached to a blue bead (free to move)
● mAbs fixed to the test stick

Question 17

Describe what happens to the test stick if a woman is pregnant

Answer 17

hCG in urine binds to mAbs attached to
a blue bead
● mAbs with hCG diffuse up dipstick
● mAbs fixed to the stick bind to hCG
● Blue line forms

Question 18

Describe what happens to the test stick if a woman is not pregnant

Answer 18

No hCG in urine so a blue line is not formed

Question 19

What is the advantage of using monoclonal antibodies to test for pathogens?

Answer 19

● Specific to one particular antigen
● Very accurate
● Quick results

Question 20

Why can monoclonal antibodies be used to target cancer cells?

Answer 20

● Cancer cells have specific antigens called ‘tumour markers’ on their membranes
● mAbs are specific to one type of antigen so can be
targeted to ‘tumour markers’ without damaging other cells

Question 21

Describe how monoclonal antibodies can be used to diagnose cancer

Answer 21

● mAbs tagged to a radioactive substance
● mAbs injected into the patient’s bloodstream
● mAbs bind to ‘tumour markers’ on cancer cells
● Emitted radiation is detected using a specialised scanner
enabling doctors to determine the location of cancer cells

Question 22

How can monoclonal antibodies be used to target drugs to cancer cells?

Answer 22

● mAbs attached to an anti-cancer drug
● mAbs injected into the patient’s bloodstream
● mAbs bind to ‘tumour markers’ on cancer cells
● Anti-cancer drug destroys cancer cells

Question 23

Why are cancer treatments that use monoclonal antibodies favoured over
traditional treatments?

Answer 23

● Radiotherapy and chemotherapy target rapidly dividing cells
● Healthy cells (e.g. hair follicle cells, bone marrow cells) are damaged as a consequence, producing unpleasant side effects
● mAbs only target cancer cells, reducing damage to normal cells

Question 24

How can monoclonal antibodies be used

to locate blood clots?

Answer 24

● mAbs tagged to a radioactive substance
● mAbs target and bind to specific proteins in blood clots
● Radiation emitted by mAbs is detected, enabling the location of blood clots to be identified